linux-kernel - Re: [Resend][PATCH] PM: Move disabling/enabling runtime PM to late suspend/early resume

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Message-ID: <CAPDyKFpXAokEr-ktU9=R+SWnfJvhRNhYPbmz-pw8-YpJiuNSSA@mail.gmail.com>
Date:	Mon, 17 Dec 2012 22:18:14 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Jiri Kosina <jkosina@...e.cz>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jan-Matthias Braun <jan_braun@....net>
Subject: Re: [Resend][PATCH] PM: Move disabling/enabling runtime PM to late
 suspend/early resume

On 16 December 2012 16:29, Alan Stern <stern@...land.harvard.edu> wrote:
> On Sun, 16 Dec 2012, Rafael J. Wysocki wrote:
>
>> On Saturday, December 15, 2012 10:16:29 PM Jiri Kosina wrote:
>> > On Sat, 15 Dec 2012, Rafael J. Wysocki wrote:
>> >
>> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> > >
>> > > Currently, the PM core disables runtime PM for all devices right
>> > > after executing subsystem/driver .suspend() callbacks for them
>> > > and re-enables it right before executing subsystem/driver .resume()
>> > > callbacks for them.  This may lead to problems when there are
>> > > two devices such that the .suspend() callback executed for one of
>> > > them depends on runtime PM working for the other.  In that case,
>> > > if runtime PM has already been disabled for the second device,
>> > > the first one's .suspend() won't work correctly (and analogously
>> > > for resume).
>> > >
>> > > To make those issues go away, make the PM core disable runtime PM
>> > > for devices right before executing subsystem/driver .suspend_late()
>> > > callbacks for them and enable runtime PM for them right after
>> > > executing subsystem/driver .resume_early() callbacks for them.  This
>> > > way the potential conflitcs between .suspend_late()/.resume_early()
>> > > and their runtime PM counterparts are still prevented from happening,
>> > > but the subtle ordering issues related to disabling/enabling runtime
>> > > PM for devices during system suspend/resume are much easier to avoid.
>> > >
>> > > Reported-and-tested-by: Jan-Matthias Braun <jan_braun@....net>
>> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> >
>> > Hi Rafael,
>> >
>> > just curious what is the reason for resend? Do you want to gather more
>> > Acks before pushing this upstream?
>>
>> Well, I thought that some people might actually look at it when they found it
>> again in their mailboxes. :-)
>
> I did look at it the first time it appeared.  It seemed to be okay, but
> I haven't tried any testing.
>
> Alan Stern
>
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I believe this should work fine for ux500 platforms, so:

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Ulf Hansson
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